@Gallup - that sounds like a summary for some documentaries I've seen on planes that have vanished. In one case, a few military fighters vanished and then a search plane vanished as well. It took like 30 years but someone reviewed the recordings and surmised that conditions led to both the fighter group and the search plane following a signal from the wrong ground base, one that was beyond their fuel range.

Since the B777 is quad redundant fly-by-wire, there are multiple power busses and backup auxiliary power generators, and battery backups. There are also mechanical horizontal situation indicating instruments and barometric altimeters, and a galvanic compass. Crews often carry hand held GPS as well.

It's all conjecture at this point, but I'm thinking fire and/or a smoke filled cockpit or something even more sinister.